BANGOR, Maine — When New England Fights brings mixed martial arts back to the Cross Insurance Center Sept. 8, the Maine-based promotion also will be hosting a retirement party of sorts. And Patrick Kelly hopes to be the one celebrating. Kelly, the 53-year-old school teacher and wrestling coach from Rockport, will take a 4-0 record into his final MMA contest when he defends his NEF amateur lightweight title against Tim Manning (2-0) in a three-round battle as part of “NEF 35: Wicked Season.” “I started this journey five years ago in Bangor [training] with Young’s MMA,” said Kelly, who will observe his 54th birthday Saturday.